The Levites were Moses" closest kinsmen. Perhaps it was for this reason, as well as their loyalty to the Lord, that they sided with Moses. Their decision and obedience ( Exodus 32:28) demonstrated their faith in God. They chose to go the way of His appointed leader, Moses, instead of following their rebellious brethren. [source][source][source]
God"s punishment of the rebels was severe ( Exodus 32:27) because of the seriousness of their offense. It was also merciful; only3 ,000 of the600 ,000 men died ( Exodus 32:28). [source][source][source]
The Levites" blessing was God"s choice of their tribe as the priestly tribe in Israel ( Numbers 3:12-13). The nation as a whole forfeited its right to be a kingdom of priests ( Exodus 19:6) by its rebellion here. [source][source][source]
"The idiom "fill the hands" [1] means "institute to a priestly office," "install," "inaugurate," and the like." [2][source]